This invention relates to ultrasonic imaging. More particularly, the present invention relates to obtaining ultrasonic images of items that are immersed in optically opaque and often, in addition, acoustically attenuating fluid media.
There are situations where it is necessary to image objects that are in an environment, such as motor oil or crude oil, or mud or other optically opaque media. For example, there is a need to inspect fuel tanks of ships or large boats that may hide contrabands. Such inspection is typically carried out using a long stick to feel through the fuel compartment to locate objects. Another example is to address the need in the oil/gas industry to visualize the down-hole drilling environment where it is necessary to monitor drill pipe, casing, and drilling collars and also to identify and then retrieve dropped testing tools, logging tools, and tubing. Currently, there is not an efficient and reliable method of accomplishing this.
The current state-of-the-art is to lower a lead impression disc down the pipeline and to then try to get an imprint of the dropped object on the lead disc. The impression produced by this method is highly inadequate and does not provide much depth of field information. This method does not result in a detailed image of any kind. It is very difficult to tell what the dropped object is from the crude impression obtained by this method.
Another method recently introduced is to lower a regular optical camera down the pipeline but this requires replacing the existing drilling fluid with clear water that takes several days in a regular well-bore and lots of adjustments before a useful image can be captured. Infrared imaging has also been explored and it has the ability to image a short distance through water and some low API crude oil but no imaging is possible through heavy oil or drilling mud. The environment encountered in well-bores for oil/gas exploration is rather harsh (corrosive fluids, high pressure and temperature) and the space available is confined, typically the size of the bore hole. It is also important to be able to obtain some depth of field information to understand the nature of the object of just getting a surface image.
The present invention provides the much-needed ability to provide clear and identifiable images of objects in optically opaque and acoustically attenuating fluids, such as drilling mud, heavy crude oil, brine/oil mixture, and bubbly fluids.